High-voltage transformer for television apparatus



Nov. 22, 1938. sc s 2,137,356

HIGH-VOLTAGE TRANSFORMER FOR TELEVISION APPARATUS Filed Dec. 9, 1955 2Sheets-Sheet l Nov. 22, 1938. K. SCHLESINGER HIGH-VOLTAGE TRANSFORMERFOR TELEVISION APPARATUS Filed Dec. 9, 1935 2 Sheets-Sheet 2 PatentedNov. 22, 1938 PATENT oFFicE,

HIGH-VOLTAGE TRANSFORMER FOR TELEVISION APPARATUS Kurt Schlesinger,Berlin, Germany, assignor to Radioaktiengesellschaft D. S. Loewe,Berlin- Steglitz, Germany Application December 9, 1935, Serial No.53,535

In Germany December 12, 1934 1 Claim.

The present invention describes a convenient arrangement of the windingsof a supply transformer in a television receiver, which is furnished ina cathode ray tube with an anode potential amounting to approximately4000-10900 volts, the arrangement being very suitable for reliableoperation in practice and for cheap construction. The invention permitsof the construction of a transformer of this kind with a minimum ofintermediate insulating layers within the windings and accordinglyhaving very small dimensions. There is taken as a, basis the knownpotential doubling connection according to Fig. 1, which, as set forthin an earlier application, offers partic'ul'ar advantages in theoperation of cathode ray tubes, because the potentials connected withthe steadying condensers l and. 2 represent in each case merely one-halfof the anode potential occurring at the cathode ray tube, and becausethe one of the same, via, the potential at I, may be employed asoperating potential for the relaxation apparatus, for whichapproximately one-half of the potential of the television tube issufficient.

Figure 1 represents a potential doubling circuit employing my invention.

Figure 2 represents a cross sectional view of the transformer.

Figure 3 shows the linking up of the transformer windings with therectifying connection system shown in diagram in Figure 1.

The transformer consists of a unitary highvoltage winding 3, andfurthermore is called upon to heat two rectifying tubes 4 and 5', whichis done by means of the windings 4 and 5. The one transformer can takeover the task of supplying the anode potential for a built-in televisionreceiver, for Which purpose it requires to be furnished with alow-voltage counter-cadence winding 6, and must heat a rectifying tube1' by means of the winding 1. It is also required of a transformer ofthis kind that the different circuits, i. e., the potentials at thecondensers l, 2 and 8, should be as independent as possible of therelative loads on the other circuits. This will only be attainable ifthe coupling between the primary windings 9, which are connected withthe mains, and the secondary windings 3 or 9 are as free of dispersionas possible.

The transformer according to Fig. 2 satisfies these requirements, andmore particularly also the requirement for ensurity against disruption,in the following manner:

According to the invention, the low voltage for the receiving portion isaccommodated in two coil members It) and II together with the primarywinding 9, 9, and at the same time these low-voltage or excitationwindings are provided on the two ends of the transformer, so that theiron core I2 is magnetized at the points of entry into the sheet metalyoke l3. The flux is then held together in the iron 12 and traverses thethird coil member l4, which carries the highvoltage windings 3, withoutdispersion. The primary winding 9, 9 is distributed over the two outermembers In and H in each case with half the number of turns. Thepotential of these windings, which are connected with the mains, is sosmall as compared with the earthed iron core that the box insulationagainst earth is not subjected to any load. The winding 6, 6 is in eachcase one-half of the anode potential winding 6 of the receiverillustrated in Fig. 1. According to the invention, the two halves areconnected with each other in the inner layers, since this connectingline l4 according to the connection system in Fig. 1 is passed to earth,and since the inner layers, therefore, do also not possess any fullpotential against earth or the mains winding 9. The intermediateinsulation 2| is, therefore, also subjected to merely very little load,and may accordingly consist of thin paper, The windings I for therectifier l of the receiver must be insulated by means of the insulation23 somewhat better, viz., towards approximately 500 volts alternatingpotential peaks against the winding 6 situated thereunder. As proved bythe normal radio art, however, this problem can still be solved reliablyin practice with a dry transformer without impregnating substances.

According to the invention, impregnation is required only in respect ofthe middle winding, which is situated in the case M and will now bedescribed. In accordance with the invention the arrangement of thewindings is in this case such that all insulations are subjected to loadonly in respect of direct potential, since it is known that a directpotential insulation is much more simple to accomplish than aninsulation with continuously varying polarization. As lowermost windingthere is accordingly located the rectifier winding 5 of the tube 5' inFig. 1, which is embedded in a thick insulating member 22. This windingrequires to withstand in relation to its surroundings a direct potentialof 4000 volts, but on the other hand no alternating potential, as it isearthed in respect of alternating current by the condenser 2 or I.Following on 5 there is the high-voltage winding 3, which may be woundin laminations without any kind of tappings. The insulation 24 alsorequires to withstand merely a direct potential of 2000 volts, since inaccordance with the invention the winding is commenced at the point 311in Fig. 1, which is earthed for alternating potential by the condenserI. It ends at the point 3b. This point is in direct connection with therectifier winding 4 of the tube 4 and may, therefore, pass into therectifier winding without intermediate insulation. This point requiresto withstand in relation to its surroundings an alternating potentialamounting in effect to 2000 volts. According to the invention, eithermerely the middle winding case M is impregnated in vacuum, viz., with aninsulating substance which remains hard at all operating temperatures,i. e., either with a hard parafline or with Bakelite or with parafiine,or the entire transformer after it has been packed with iron may beplaced in a large impregnating vessel and impregnated in vacuum at asufiiciently high temperature above the melting point of the insulatingsubstance. Measurements in respect to a transformer of this kind in theconnection set forth in Figs. 1 and 2 result in an independent nature ofthe single circuits for the receiver on the one hand and tube screenapparatus on the other hand better than 5%. In a television receiverhaving built-in receiving superhet with an amplification of more than100,000 there were also no longer noticed crackling noises such asfrequently occurs by spluttering action in highfrequency transformers.This is due primarily to the lack of alternating potential load on theinsulation of the transformer. The thickness of wire of the singlehigh-voltage windings 9, 6 and 3 is, in the manner known per se, inproportion to the currents traversing the same. A transformer of thiskind mastered in practice 150 watts with a primary current intake of 1ampere or a supply of 0.1 ampere to the receiving portion, 0.015 ampereto the screen and 0.05 ampere to the television tube. The thickness ofthe wire was, in

respect of the primary winding 9, 0.6 mm., in respect of the receivingwinding 6, 0.2 mm., and in respect of the high-voltage winding 3, 0.1mm. and, as may readily be calculated, are in proportion to the roots ofthe stated current loads. In spite of the high output referred to thetemperature accordingly also remained below 60'.

I claim:

In a supply apparatus containing two rectifier devices includingrectifier tubes having cathodes and anodes, a transformer having an ironcore, a primary winding and several secondary windings for supplying theheating circuits and the anode circuits of said rectifier tubes, one ofsaid rectifier devices furnishing a direct current potential of severalthousand volts and consisting of a potential doubling rectifier circuitwith two rectifier tubes and two condensers and the other furnishing adirect current potential of several hundred volts by a single rectifierwith two anodes, three separate winding spaces arranged side by side onthe iron core, the middle space containing only the secondary windingcorresponding to said high potential rectifier and the outer spacescontaining said primary winding and said secondary windingscorresponding to the low potential rectifier, the high potentialsecondary winding being arranged between two halves of the correspondingheating current winding, each half of said primary winding beingarranged next to the iron core, the two halves of the low potentialsecondary windings being arranged over said primary winding and thecorresponding heating winding being arranged over said anode currentwinding, the two halves of said anode-current windings connectedtogether on the inside next to said primary windings in order that allinsulations between said secondary windings will be loaded only inrespect to high direct potentials but not to high alternatingpotentials.

KURT SCI-ILESINGER.

